1. Field of the Invention (Technical Field)
The present invention relates to cyclic natriuretic peptide constructs which include a plurality of amino acid residues, one or more ring-constrained amino acid surrogates and optionally one or more prosthetic groups, which constructs bind a natriuretic peptide receptor and may be employed for therapeutic purposes.
2. Background Art
The natriuretic peptide system has been extensively explored since the identification of the human atrial natriuretic peptide (ANP) sequence and gene structure in 1984. ANP is sometimes also called “ANF”, or atrial natriuretic factor. ANP is part of the natriuretic peptide system, which in humans involves an ANP gene, which through differences in post-translational processing results in both ANP and urodilatin, a gene which produces BNP, or brain natriuretic peptide, and a gene which produces CNP, or c-type natriuretic peptide. ANP, urodilatin, BNP and CNP are each ring structures, with a 17 amino acid loop formed by a cysteine-cysteine disulfide linkage. The amino acid sequence and structure of human ANP (hANP) is shown in FIG. 1. ANP, urodilatin, BNP and CNP are closely related, differing by some five or six amino acids within the ring, though the N- and C-terminal tails are substantially different.
There are three known natriuretic peptide receptors called natriuretic peptide receptors A, B and C (NPRA, NPRB and NPRC). NPRA and NPRB are linked to guanylyl cyclases, while NPRC is a G-protein linked clearance receptor. ANP, BNP and CNP are the primary endogenous mammalian natriuretic peptides identified to date. However, there are a number of non-mammalian natriuretic peptides that have been identified and may have therapeutic application in mammals. These include salmon natriuretic or cardiac peptide (sCP), ventricular natriuretic peptide (VNP), a cardiac natriuretic peptide identified in eels and a variety of fish, dendroaspis natriuretic peptide (DNP), a natriuretic peptide identified in mamba snake venom, and three natriuretic-like peptides (TNP-a, TNP-b, and TNP-c) isolated from taipan snake venom. See generally Tervonen V, Ruskoaho H, Lecklin T, Ilves M, Vuolteenaho O, Salmon cardiac natriuretic peptide is a volume-regulating hormone. Am. J. Physiol. Endocrinol. Metab. 283:E353-61 (2002); Takei Y, Fukuzawa A, Itahara Y, Watanabe T X, Yoshizawa Kumagaye K, Nakajima K, Yasuda A, Smith M P, Duff D W, Olson K R. A new natriuretic peptide isolated from cardiac atria of trout, Oncorhynchus mykiss. FEBS Lett. 414:377-80 (1997); Schweitz H, Vigne P, Moinier D, Frelin C, Lazdunski M. A new member of the natriuretic peptide family is present in the venom of the green mamba (Dendroaspis angusticeps). J. Biol. Chem. 267:13928-32 (1992); Lisy O, Jougasaki M, Heublein D M, Schirger J A, Chen H H, Wennberg P W, Burnett J C. Renal actions of synthetic dendroaspis natriuretic peptide. Kidney Int. 56:502-8 (1999); and Fry B G, Wickramaratana J C, Lemme S, Beuve A, Garbers D, Hodgson W C, Alewood P. Novel natriuretic peptides from the venom of the inland (Oxyuranus microlepidotus): isolation, chemical and biological characterisation. Biochem. Biophys. Res. Comm. 327:1011-1015 (2005).
ANP is endogenously secreted predominately in response to increased atrial pressure, but other factors, including cytokine receptor stimulation, may contribute to endogenous secretion. Once released, ANP is a hormonal regulator of blood pressure, sodium and fluid homeostasis, providing vasorelaxant effects, affecting cardiovascular remodeling, and the like. Thus ANP, including endogenous ANP, is effective in congestive heart failure and other cardiovascular disease, in part by providing a defense against a chronically activated renin-angiotensin-aldosterone system. Circulating ANP is rapidly removed from the circulation by two mechanisms, binding to a natriuretic peptide receptor and enzymatic degradation.
Human ANP is also referred to as wild-type human ANP, hANP, ANP(1-28) and ANP(99-126) (the later referring to the relevant sequence within proANP(1-126), which is normally cleaved at Arg98-Ser99 in the C-terminal region during secretion). Hereafter human ANP is sometimes referred to as “hANP.”
In general, natriuretic peptides and variants thereof are believed to have utility in the treatment of congestive heart failure, renal hypertension, acute kidney failure and related conditions, as well as any condition, disease or syndrome for which a diuretic, natriuretic and/or vasodilatory response would have a therapeutic or preventative effect. One review article describing natriuretic peptides, including ANP, and use of the natriuretic peptide system in heart failure is Schmitt M., Cockcroft J. R., and Frenneaux M. P. Modulation of the natriuretic peptide system in heart failure: from bench to bedside? Clinical Science 105:141-160 (2003).
A large number of ANP mimetics and variations have been made, some of which are substantially reduced in size from ANP. On ANP version that is reduced in size yet is biologically active is the 15-mer disulfide cyclic peptide H-Met-cyclo(Cys-His-Phe-Gly-Gly-Arg-Met-Asp-Arg-Ile-Ser-Cys)-Tyr-Arg-NH2 (SEQ ID NO:1) as described in Li B, Tom J Y, Oare D, Yen R, Fairbrother W J, Wells J A, Cunningham B C. Minimization of a polypeptide hormone. Science 270:1657-60 (1995). This 15-mer peptide is commonly referred to as “mini-ANP”.
A number of patents and patent applications have been filed on different synthetic mimics of natriuretic peptides, asserted to be superior to wild-type natriuretic peptides based on one or more factors. These include the constructs disclosed in the following U.S. Pat. Nos. 4,496,544; 4,609,725; 4,656,158; 4,673,732; 4,716,147; 4,757,048; 4,764,504; 4,804,650; 4,816,443; 4,824,937; 4,861,755; 4,904,763; 4,935,492; 4,952,561; 5,047,397; 5,057,495; 5,057,603; 5,091,366; 5,095,004; 5,106,834; 5,114,923; 5,159,061; 5,204,328; 5,212,286; 5,352,587; 5,376,635; 5,418,219; 5,665,704; 5,846,932; 5,583,108; 5,965,533; 6,028,055; 6,083,982; 6,124,430; 6,150,402; 6,407,211; 6,525,022; 6,586,396 and 6,818,619; and in the following U.S. Patent Application Publications: 2004/0002458; 2004/0063630; 2004/0077537; 2005/0113286; 2005/0176641; 2006/0030004. In addition, various non-U.S. patents and patent applications disclose constructs, including: WO 85/04870; WO 85/04872; WO 88/03537; WO 88/06596; WO 89/10935; WO 89/05654; WO 90/01940; WO 90/14362; WO 92/06998; WO 95/13296; WO 99/08510; WO 99/12576; WO 01/016295; WO 2004/047871; WO 2005/072055; EPO 0 291 999; EPO 0 323 740; EPO 0 341 603; EPO 0 350 318; EPO 0 356 124; EPO 0 385 476; EPO 0 497 368; and EPO 0 542 863. Chimeric natriuretic peptides, such as a peptide call “vasonatrin peptide” and described as a chimera of ANP and CNP, are described, as in U.S. Pat. No. 5,583,108, or in U.S. Pat. Nos. 6,407,211 and 6,818,619, disclosing chimeric peptides of dendroaspis. The teachings of each of the foregoing patents and patent applications are incorporated by reference as if set forth in full.
There is one natriuretic peptide product approved by the Food and Drug Administration in the United States, sold under the generic name nestiritide and the tradename Natrecor® (Scios Inc.). This is a human B-type natriuretic peptide manufactured from E. coli using recombinant DNA technology. This product is approved only for intravenous infusion for treatment of patients with actutely decompensated congestive heart failure who have dyspnea at rest or with minimal activity. While effective, the pharmacokinetics and half-life of nestiritide are such that the product can only be employed by intravenous infusion, which limits use of the drug to a hospital or skilled medical center setting.
Notwithstanding the large number of compounds that have been developed, virtually none are commercialized or in active clinical development. There is a substantial need for products with improved characteristics, including improved potency, half-life, modes of administration, bioavailability or prolonged duration of effect, which products are effective for one or more therapeutic indications, and which preferably may be administered on an out-patient basis.